Induced Land Use Emissions due to First and Second Generation Biofuels and Uncertainty in Land Use Emission Factors

Much research has estimated induced land use changes (ILUCs) and emissions for first generation biofuels. Relatively little has provided estimates for the second generation biofuels. This paper estimates ILUC emissions for the first and second generation biofuels. Estimated ILUC emissions are uncertain not only because their associated land use changes are uncertain, but also because of uncertainty in the land use emission factors (EFs). This paper also examines uncertainties related to these factors. The results suggest that converting crop residues to biofuel has no significant ILUC emissions, but that is not the case for dedicated energy crops. Use of dedicated energy crops transfers managed natural land and marginal land (cropland-pasture) to crop production. Producing biogasoline from miscanthus generates the lowest land requirement among alterative pathways. The largest land requirement is associated with switchgrass. The difference is due largely to the assumed yields of switchgrass and miscanthus. The three major conclusions from uncertainty in emissions analyses are (1) inclusion or exclusion of cropland-pasture makes a huge difference; (2) changes in soil carbon sequestration due to changes in land cover vegetation play an important role; and (3) there is wide divergence among the emission factor sources, especially for dedicated crop conversion to ethanol. 1. Introduction The land use consequences of global biofuel programs and their contributions to GHG emissions have been the focal point of many debates and research studies in recent years. Research studies in this field usually estimate ILUC emissions in two phases. They first estimate ILUCs due to biofuel production using either partial or general equilibrium models. Then they apply land use emission factors (EFs), which measure vegetation and soil carbon fluxes and are obtained from biophysical models, to calculate the ILUC emissions given the estimated ILUCs. Both of these phases are subject to uncertainties. Several papers examined major uncertainties related to the estimates for ILUCs and their geographical distributions. Wicke et al. [1] reviewed major studies in this area and highlighted deficiencies of economic models used to assess the ILUCs due to biofuels and their corresponding uncertainties. However, most of these studies focused on the land use emissions due to first generation biofuels such as corn ethanol, sugarcane ethanol, and biodiesel. Few attempts have been made to estimate these emissions for second generation biofuels which convert cellulosic materials into liquid